error:Deminsion 2 is fixed on left hand side but varies on right([1x1]}~=([1x:?])

While convertio=ng my code fro matlab to c++ I am showing some error; which says Deminsion 2 is fixed on left hand side but varies on right([1x1]}~=([1x:?])

this is my code which i was trying to convert where T is 1x401 and Y is 1x21

    function summ = u_sum(T,Y)
    summ = 0;
    for i=1:20
        lmd = (2*i+1)*pi;
        a = 4/((lmd)^3);
        b = sin(lmd*Y);
        c = exp(-(lmd^2)*T);
        summ = summ + (a*b*c); 
    end
end

[Sameeksha Singh]

Please reply asap, thankyou

Answer 1

[Mathieu NOE]

hi

there is something wrong in your code

a, b,c have different dimensions so the product a*b*c is not possible (summ = summ + (a*b*c); )

Name Size Bytes Class

T 1x401 3208 double array

Y 1x21 168 double array

a 1x1 8 double array

b 1x21 168 double array

c 1x401 3208 double array

i 1x1 8 double array

lmd 1x1 8 double array

summ 1x1 8 double array

[Sameeksha Singh]

Do you have any solution? @Mathieu NOE as I am new to Matlab, and I have to complete a project

[Mathieu NOE]

as mentionned above by Walter , you have to decide how to index Y and T in the a,b,c terms , (if they must all be scalars)

I cannot guess that for you , because I don't know what your summ computation is supposed to do

[Sameeksha Singh]

@Mathieu NOE thankyou so muchh

Answer 2

[Walter Roberson]

    summ = 0;

That is a scalar. Once that assignment is made, the variable cannot grow larger..

     b = sin(lmd*Y);

That uses all of Y, so b would be 1x21.

summ = summ + (a*b*c);

scalar plus scalar times vector times scalar gives vector right hand side. But you try to assign to summ which has been created as a scalar. When you are doing code generation, variables cannot grow unless you use special forms.

If you want a vector output then initialize summ to zeroes(size(Y)).

I suspect that you might have wanted to index Y in the loop

[Sameeksha Singh]

Thanks @Walter Roberson, yes I want index Y in the loop